19. Gaseous pollutants

Gaseous pollutants are emitted during the direct combustion of fossil fuels. These are primary pollutants. They can interact with the environment to generate secondary pollutants. The main primary pollutants are carbon monoxide CO, sulfur oxides SO _x (SO ₂ and SO ₃ ), nitrogen oxides NO _x (NO, NO ₂ , N ₂ O, N ₂ O ₅ and NO ₃ ), particulates (soot particles and fine ash), unburned hydrocarbons.

• Carbon monoxide is produced by the incomplete...